A card cage is a box-shaped chassis or frame having a number of parallel card slots or bays into which printed circuit cards can be received. A card cage may have metal sidewalls to provide electromagnetic interference (EMI) shielding. Each slot is commonly defined by a pair of card guides: an upper card guide and a lower card guide. When a user inserts a printed circuit card, the upper edge of the printed circuit card engages a slot in the upper card guide while the lower edge of the printed circuit card engages a slot in the lower card guide. The user slides the printed circuit card in the card guides into the card cage until a connector on the rear edge of the printed circuit card mates with a backplane connector on a backplane at the rear of the card cage. A backplane commonly comprises a printed circuit board on which are mounted a number of such backplane connectors, each aligned with one of the card slots or bays. This backplane printed circuit board provides electrical signal interconnections among the backplane connectors.
The printed circuit cards that are inserted in the card cage commonly have faceplates mounted on the front edge of the card. Faceplates of printed circuit cards in adjacent slots abut one another when the spacing between adjacent slots is the minimum that is sufficient to accommodate the width of the faceplates. Printed circuit cards can have faceplates of various widths. It is commonly necessarily to include a group of printed circuit cards having different widths in an electronic system. To mount such a group of printed circuit cards in a card cage, not only must the card cage slots be configured to accommodate the different faceplate widths but the spacing of the backplane connectors on the backplane must be configured accordingly.